Organosilicon compounds are produced by formation of Si—C bonds. Especially, hydrosilylation describes the addition reaction between an organosilicon compound having a Si—H bond and an unsaturated hydrocarbon such as olefin or acetylene derivatives. Typically, the reaction is performed in the presence of a metal catalyst. A hydrosilylation reaction of an olefin may be represented by Scheme 1:

For the metal complex catalyst, group 10 transition metal compounds are known to be effective for the hydrosilylation reaction. In particular, platinum-based compounds are industrially widely used as catalyst. Historically, chloroplatinic acid (H2PtCl6/iPrOH) was first known to be an effective catalyst in the hydrosilylation reaction in 1957 [Speier, J. L. and Hook, D. E. U.S. Pat. No. 2,823,218 (1958); Speier, John L., Webster, James A. and Barnes, Garrett H. J. Am. Chem. Soc. 1957, 79, 974-9]. Bailey, D. L. and Snyder, N.Y. reported catalytic activity of platinum supported on alumina (Pt@g-alumina) [U.S. Pat. No. 2,970,150, 1961]. However, the hydrosilylation reaction described in the above US patents is economically unfavorable because a large quantity of platinum catalyst has to be used.
At present, in most industrial-scale preparation of organosilicon compounds by hydrosilylation, the Karstedt catalyst, i.e. a platinum complex in oxidation state 0, is used. The general formula of the Karstedt complex is Pt2[(CH2═CH)Me2Si—O—SiMe2(CH═CH2)]3 [Karstedt, B. D., U.S. Pat. No. 3,775,452, 1973]. The Karstedt catalyst has a drawback that it is unstable during hydrosilylation, which can be ascertained by the precipitation of metallic platinum in the reaction medium and the formation of insoluble colloid. The instability of the catalyst in the reaction medium may result in decrease in catalytic activity. Furthermore, the instability of the Karstedt catalyst induces the formation of colored hydrosilylation products, thereby resulting in a cloudy, colored solution. Besides, because of production of byproduct, the Karstedt catalyst gives a low yield from hydrosilylation reaction. In addition to the desired product, byproducts resulting from isomerization and/or hydrogenation of the olefinic double bond are obtained.
In order to solve the problems of the Karstedt catalyst, Marko et al. reported a new catalyst [WO 2001/42,258], which is a metal complex
containing an unsaturated 5-membered N-heterocyclic carbene (U-NHC5). The patent restrictively describes hydrosilylation of a hydrosilane ((bissilyloxy)hydrosilane: Me3SiO—SiHMe—OSiMe3). The hydrosilane is a component of hydrosilicone oil and is widely used in the silicone industry. Although the carbene metal complex catalyst developed by Marko et al. is advantageous in that it is relatively stable under air and the metal complex structure is maintained during storage and hydrosilylation, catalytic activity of hydrosilylation is unsatisfactory.